1. Field of the Invention:
This invention pertains generally to a process for removing undesired polysaccharide and other hydrophilic constituents from hydrophobic compositions containing same and, in particular to the removal of polysaccharide constituents and other materials from glycoside surfactant/hydrophobic alcohol or other hydrophobic solvent compositions or from polysaccharide-containing mixed hydrophobic alcohol/glycoside surfactant compositions. In one embodiment, the invention involves a glycoside surfactant manufacturing process wherein the indicated polysaccharide removal technique is applied to a crude polysaccharide-containing hydrophobic alcohol/glycoside surfactant reaction product mixture prior to the evaporative separation of the hydrophobic alcohol from the desired glycoside surfactant product.
In accordance with the process there is provided certain novel glycoside surfactant compositions which have an average of at least 9 carbon atoms in the hydrophobic aglycone substituent thereof and an average degree of polymerization (D.P.) of at least 1.2 and which are essentially free of (i.e., contain, on a total glycoside surfactant weight basis, less than 0.5 weight percent of) undesired polysaccharide constituents and which contain, on a total glycoside surfactant weight basis, less than 5 (preferably less than 1) weight percent of polyglycoside species or constituents having a degree of polymerization of 10 or above. The process is useful for purifying alkyl polyglycoside products to produce a refined material for special uses. 2. Statement of Related Art:
Long chain alkyl monoglycosides and long chain alkyl polyglycosides and mixtures thereof (hereinafter generically referred to as "glycoside surfactants") are known materials, are known to be surface active in character and are known to be useful in a wide variety of household and industrial applications. Moreover, it is also known that glycoside surfactants can be prepared by reacting a long chain alcohol with a saccharide reactant (e.g., a monosaccharide or a material hydrolyzable to a monosaccharide) at an elevated temperature in the presence of an acid catalyst.
Processes for preparing alkyl glycoside compositions are disclosed in U.S. Pat. No. 3,219,656 to Boettner (issued Nov. 23, 1965); U.S. Pat. No. 3,547,828 to Mansfield et al. (issued Dec. 15, 1970); U.S. Pat. No. 3,598,865 to Lew (issued Aug. 10, 1971); U.S. Pat. No. 3,707,535 to Lew (issued Dec. 26, 1972); U.S. Pat. No. 3,772,269 to Lew (issued Nov. 13, 1973); U.S. Pat. No. 3,839,318 to Mansfield (issued Oct. 1, 1974); U.S. Pat. No. 4,349,669 to Klahr (issued Sept. 14, 1982); U.S. Pat. No. 4,393,203 to Mao et al. (issued Jul. 12, 1983); U.S. Pat. No. 4,472,170 to Hellyer (issued Sept. 18, 1984); U.S. Pat. No. 4,510,306 to Langdon (issued Apr. 9, 1985); U.S. Pat. No. 4,597,770 to Forand et al. (issued Jul. 1, 1986); U.S. Pat. No. 4,704,453 to Lorenz et al. (issued Nov. 3, 1987): U.S. Pat. No. 4,713,447 to Letton (issued Dec. 15, 1987); published European Application No. 83302002.7 (EPO Publication No. 0092355; Vander Burgh et al; published Oct. 26, 1983); published European Application No. 83200771.0 (EPO Publication No.0096917; Farris; published Dec. 28, 1983); and published European Application No. 84303874.6 (EPO Publication 0132043; published Jan. 23, 1985).
During the course of the aforementioned acid-catalyzed saccharide reactant/long chain alcohol reaction process, there is usually employed a substantial stoichiometric excess of the long chain alcohol reactant. The resulting reaction product mixture as initially made (i.e., without any intervening separation, fractionation or purification operations) typically contains a substantial quantity of residual unreacted long chain alcohol, the monoglycoside of the long chain alcohol as the predominant glycoside molecular species on a mole percentage basis, the various higher degree of polymerization long chain alcohol polyglycoside species in progressively decreasing mole percentage amounts or proportions, substantial but variable amounts of polysaccharide by-products which do not have long chain alcohol molecules chemically attached (or covalently bonded) thereto and miscellaneous materials such as catalysts, processing aids and the like.
In accordance with the various prior art references, it has been conventional practice to remove the residual unreacted long chain alcohol from the indicated reaction mixture via various techniques such as vacuum distillation, organic solvent (e.g., acetone) extraction or fractionation, and thin (or wiped) film evaporation.
If the long chain (fatty) alcohol is removed from the reaction mixture by one of the distillation or evaporation methods, the polysaccharide by products and any other materials with low volatility remain in the alkyl glycoside product.
The presence of the aforementioned polysaccharide byproducts and other impurities in the long chain (or "fatty") alcohol-containing reaction mixture can result in the development of unacceptable properties (e.g. high viscosities) and/or in the development of dark-colored insoluble particulate matter and/or in fouling of heat transfer surfaces during evaporative removal of the unreacted fatty alcohol from the reaction mixture using wiped or thin film evaporation equipment.
In addition, certain applications require an alkyl glycoside surfactant product with a low content of non-alkyl glycoside materials. The method of the present invention can be used to reduce the concentration of certain non-alkyl glycoside hydrophilic or water miscible components in an alkyl glycoside surfactant product.